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Biomedical subjects

J L Miramand

Publications and source records attributed to J L Miramand.

9 recordsLinked to original sources
PubMed1995

Cardiovascular changes during acute episodic repetitive hypoxic and hypercapnic breathing in rats.

It has been shown that chronic repetitive ambient hypoxia, simulating pulmonary gas disturbances observed in apnoea, leads to systemic hypertension in rats. However, the relative roles of hypoxia (HO), hypercapnia (HC), gas stress and vigilance on the cardiovascular changes have not yet been demonstrated. The aim of this study was to investigate the acute haemodynamic changes observed during the repetitive inhalation of various gas mixtures in rats for HO alone and HO+HC, and to analyse the effects of vigilance and of the stress of gas administration. We studied 6 unanaesthetized Wistar rats chronically instrumented with an aortic catheter. Nitrogen, nitrogen+CO2 mixtures and compressed air were randomly administered in a Plexiglass chamber for 10 s and then flushed by compressed air for 20 s. Two cycles were repeated every min for 10 to 12 min. The inhaled gas fractions (FI,O2,FI,CO2) were monitored by O2 and CO2 analysers. Blood pressure (BP) was measured by a P23XL transducer. The blood gases were analysed by a 1306 IL meter. In control experiments, with compressed air alone, there were no significant acute changes in heart rate (HR) and BP. During HO there were no changes in HR or BP at FI,O2 values from 0.05-0.14, whilst at FI,O2 values from 0-0.05 systolic blood pressure (SBP) rose significantly (+25.3 +/- 25.7 (SD) mmHg) and HR decreased (-93.8 +/- 124.1 bpm). During HOHC, SBP rose (+35.1 +/- 26.4 mmHg) and HR decreased (-139.3 +/- 75.7 bpm), significantly more than in HO alone. SBP was linearly correlated with Pa,O2 during HO (r = 0.53) and also during HOHC (r = 0.44) and was not directly related to Pa,CO2 which has, nevertheless, an additive effect to HO. SBP rose with each challenge significantly more when the rats were awake than when asleep (behavioural sleep). We conclude that in this acute repetitive inhalation model, the rise in SBP is not related to gas stress or to Pa,CO2 but to a decrease in Pa,O2 and is enhanced by wakefulness.

Acute Disease↗
PubMed1994

Ventilatory conditioning by self-stimulation in rats: a pilot study.

This article describes an experimental attempt to condition breathing pattern in rats. In this experiment, a freely moving rat was first rewarded by an electrical stimulation of the medial forebrain bundle whenever inspiratory duration (TI) exceeded 300 ms. A bidirectional control was then used: TIs longer than 400 ms were rewarded, and then TIs shorter than 300 ms were rewarded. The frequency of TIs longer than 300 ms increased when this event was rewarded, further increased when TIs above 400 ms were rewarded, and decreased during reversal conditioning (TI < 300 ms). At the beginning of the experiment, stimulation caused increased arousal and motor activity, but after prolonged conditioning, the brain stimulation was associated with quiet wakefulness. Although the general procedure appears to be well-suited to the experimental study of voluntary breathing, some possible improvements are suggested for further, more extensive investigations.

Animals↗
PubMed1994

Measurement of respiratory times in freely moving rats.

A catheter was threaded beneath the skin from the trachea to an opening on the top of the skull. It conducted a small fraction of the ventilatory flow to an external miniaturized transducer, which was composed of a heating element surrounded by two thermocouples. During inspiration, the heating element heated the inner thermocouple, whereas during expiration it heated the outer one. A square signal synchronous with breathing was obtained from the difference in temperature at the two probing sites. Inspiratory and expiratory times were calculated from this signal. This device has been tested with calibrated flows, and compared with head-out plethysmography. It may be easily adapted for ventilatory measurements in any small mammal.

Animals↗
PubMed1992

Dose-related bronchodilator response to aerosolized salbutamol (albuterol) in ventilator-dependent premature infants.

We used a placebo-controlled standardized protocol to define the dose-response relationship to the beta-adrenergic bronchodilator salbutamol (albuterol) in 10 ventilator-dependent premature infants at a postnatal age of 13.3 +/- 4.9 days. Passive respiratory system resistance and compliance were measured at baseline and 10 minutes after administration of salbutamol via a metered-dose inhaler and spacer device. Salbutamol caused a significant dose-related response with a 33% mean decrease in respiratory system resistance (p less than 0.05) and a 67% mean increase in respiratory system compliance (p less than 0.001). In seven and six patients, respectively, 100 micrograms of salbutamol caused significant improvement in resistance and compliance; 200 micrograms was required in the remainder, but one patient had no improvement in compliance. Oxygen saturation increased linearly with the increase in compliance. In 7 of the 10 infants, the duration of action of 200 micrograms of salbutamol on the following day was 3 hours. We conclude that bronchodilator treatment may be useful in the management of ventilator-dependent neonates with respiratory distress syndrome.

Aerosols↗
PubMed1985

Effects of hyperthermia on normal or neoplastic rat liver.

An experimental study was conducted in rats to evaluate the sensitivity of the liver to infrared hyperthermia. A 15-min hyperthermia session treating only the liver was done in rats with a normal hepatic parenchyma and in rats with hepatocarcinoma induced by chronic 3'-diethylaminoazobenzene intoxication, at various ranges of intrahepatic temperature. In normal rats, 40-42 degrees C hyperthermia was well tolerated, but the mortality rate increased when the intrahepatic temperature exceeded 42 degrees C. In rats with tumors, a 40-42 degrees C hyperthermia session was well tolerated in case of small tumors, but resulted in a high mortality rate in case of large tumors. In all cases, death occurred as a consequence of liver injury. This study using a simple method of hyperthermia defines the thermosensitivity of the neoplastic or normal rat liver and provides a basis for further investigations on the effect of hyperthermia on experimental liver tumors.

Animals↗
PubMed1985

[Behavior of urinary magnesium in comparison with urinary calcium and oxaluria in rats subjected to portacaval anastomosis].

Rats with a portacaval anastomosis are known to be susceptible to develop uric acid stones. The present studies were undertaken to investigate urinary Mg, Ca and oxalate excretion in such rats. We found that their Mg excretion was doubled, Ca excretion tripled, and oxaluria somewhat decreased. The Ca crystallization attributed to the increased Ca2+ in the urine is, therefore, somewhat held in check by the increased presence of Mg in the urine and by decreased oxalates.

Animals↗
PubMed1985

[Increase in urinary uric acid in the rat following portacaval shunt. The action of clofibrate].

Two successive experiments on rats confirm that a portocaval shunt leads to a substantial increase in uricosuria, which does not climax in the first week postoperatively. Clofibrate, an inductive liver enzyme, significantly reduces the uricosuria, but only after a certain timelag. Uricosuria, the degree of which varies with individual rats, leads to crystallization of uric acid, mainly in the form of ammonium urate, but polyuria secondary to portocaval shunt tends to inhibit the crystallization. A reduced water intake one day out of two facilitates the crystallization after a portocaval shunt.

Animals↗
PubMed1981

A device for jointless connections with unrestrained animals.

An apparatus is described allowing multichannel connection with unrestrained animals without using joints. The twisting of the connection lines caused by the rotation of the animal in its cage is detected by means of a torsion wire connected to an electronic device. This provokes a temporized rotation of the bottom of the cage in the opposite direction in order to untwist the lines.

Animal Husbandry↗